1. Field of the Invention
The present invention relates to the field of telecommunications. More particularly, the present invention relates to secure asynchronous transfer mode (ATM)-based telecommunications networks.
2. Background Information
In current time division multiplexed (TDM)-based telecommunications networks, signaling messages for managing telephone calls are carried on a network different from a network carrying the telephone conversations themselves. In fact, the control network, which carries the messages that establish and tear down connections, is physically separate from the bearer network, which carries the customer, or bearer traffic. In other words, control and bearer traffic are segregated. One reason for the segregation is to prevent unauthorized access to voice connections. Control traffic in the typical voice network will be referred to as narrowband control traffic, in contrast to ATM control traffic.
A new voice trunking system using ATM technology has been proposed in U.S. patent application Ser. No. 09/287,092, entitled “ATM-Based Distributed Virtual Tandem Switching System.” The architecture represents a new paradigm of networking that requires re-thinking network security. In this system, shown in FIG. 1, voice trunks from end office switches 16, 18 are converted to ATM cell streams by a first or second trunk inter-working function (T-IWF) device 10. The T-IWFs 10 are distributed to each end office 16, 18, and are controlled by a centralized control- and signaling inter-working function (CS-IWF) device 12. The CS-IWF 12 performs call control functions as well as conversion between the narrowband Signaling System No. 7 (SS7) protocol and a broadband signaling protocol. The T-IWFs 10, CS-IWF 12, and an ATM network 14 of ATM switches form the ATM-based distributed virtual tandem switching system. According to this voice trunking over ATM (VTOA) architecture, trunks are no longer statistically provisioned as DSO time slots. Instead, the trunks are realized through dynamically established switched virtual connections (SVCs), thus eliminating the need to provision separate trunk groups to different destinations, as done in TDM-based trunking networks.
In the VTOA architecture, narrowband control and bearer traffic are still segregated. ATM control and bearer traffic, however, are not carried on distinct, physically separate networks. That is, signaling messages that control switched virtual connections (SVCs) traverse the same communications links as the bearer traffic carried by the SVCs. Thus, new security risks are present. For example, unauthorized access to the ATM SVCs should be prevented, just as unauthorized access to voice connections in the typical network is currently prevented.
Moreover, in complex multi-service multi-carrier networks, additional security requirements are required. For example, interception and malicious alteration or replay of sensitive operations, administration, and maintenance (OAM) and control messages should be prevented.
Consequently, current security practices and infrastructures must be adapted to make certain that deployments of this new architecture are as secure as the existing TDM voice network.